The present invention relates to a process for preparing optically active halogenated cyclopropane derivatives which are useful as synthetic intermediates for the preparation of synthetic new quinolone antibacterial agents having excellent activity and safety.
Among the new quinolone antibacterial agents having excellent antibacterial activity, synthetic antibacterial agents having a fluorocyclopropyl group at the 1-position of the quinolone nucleus have both excellent antibacterial activity and safety, and accordingly, they are expected as clinically useful drugs (Japanese Patent Unexamined Publication (KOKAI) No. (Hei) 2-231475/1990). Optically active 2-fluorocyclopropanecarboxylic acid and derivatives thereof having a specific stereochemical configuration, i.e., (1S, 2S), are important as synthetic intermediates for these compounds.
(1S,2S)-2-fluorocyclopropanecarboxylic acid is heretofore prepared by the steps of addition of bromofluorocarbene to butadiene to produce 1-bromo-1-fluoro-2-vinylcyclopropane; oxidation of the vinyl group to obtain a carboxylic acid and then esterification and successive debromination of the resulting product; separation of a cis-isomer from the resulting reaction mixture by distillation; hydrolysis of the ester group of the cis-isomer to afford a carboxylic acid; and optical resolution of the resulting carboxylic acid (see, the reaction scheme set out below). 
Another method for preparing (1S,2S)-2-fluorocyclopropanecarboxylic acid is known which comprises the steps of reacting a vinyl halogenide with a diazoacetic acid derivative in the presence of a variety of metal catalysts, optionally followed by additional dehalogenation reaction, separation of stereoisomers, and optical resolution (Japanese Patent Unexamined Publication (KOKAI) No. (Hei) 6-949911994 and Japanese Patent Unexamined Publication (KOKAI) No. (Hei) 5-194323/1993). However, no metal catalyst having one or more chiral ligands was used in the aforementioned processes.
These preparing processes involve the step of optical resolution of the desired optically active compound having (1S,2S)-configuration after the preparation of the racemic 1,2-cis-2-fluorocyclopropanecarboxylic acid derivative, and the (1R,2R)-isomer, which comprises the half of the racemate, have to be removed as waste matter. Therefore, these processes are not efficient from economical and industrial viewpoints.
The object of the present invention is to provide an efficient and convenient process for preparing optically active halogenated cyclopropane derivatives which are useful for the manufacture of the optically active (1S,2S)-2-fluorocyclopropane-carboxylic acid or derivatives thereof. More specifically, the object of the present invention is to provide a process for preparing the aforementioned optically active halogenated cyclopropane derivatives by a stereoselective reaction using readily available starting materials.
The inventors of the present invention conducted various studies to achieve the foregoing object, and as a result, they found that a 2-fluoro-2-chlorocyclopropanecarboxylic acid derivative can be obtained stereoselectively and in high yield by reacting a diazoacetic acid derivative with 1-fluoro-1-chloroethylene, for example, in the presence of a metal catalyst having one or more chiral ligands. The inventors of the present invention also found that the optically active 2-fluoro-cyclopropanecarboxylic acid derivatives having the desired stereochemical configuration, i.e., (1S,2S), can be prepared in high yield by subjecting the aforementioned 2-fluoro-2-chlorocyclopropanecarboxylic acid derivative to dehalogenation reaction. The present invention was achieved on the basis of these findings.
The present invention thus provides a process for preparing compounds represented by the following general formula (I): 
wherein:
X represents chlorine atom, bromine atom, or iodine atom;
R represents a C1-10 (containing 1-10 carbon atoms) alkyloxy group which may have one or more halogen atoms or one or more C1-10 alkyloxy groups;
an aralkyloxy group constituted by one or more aryl groups which may have a substituent(s) and a C1-10 alkyloxy group;
an aryloxy group having an aryl groups which may be substituted;
a C1-10 alkylthio group which may have one or more halogen atoms;
an aralkylthio group constituted by an aryl group which may have a substituent(s) and a C1-10 alkylthio group;
amino group; or
a substituted amino group which has one or more substituents selected from the group consisting of a C1-10 alkyl group, an aryl group which may be substituted, an aralkyl group constituted by an aryl group which may have a substituent(s) and a C1-10 alkyl group, and an acyl group;
provided that substituents of the substituted aryl groups are selected from the group consisting of a halogen atom, a C1-10 alkyl group, a C1-10 halogenoalkyl group, a C1-10 alkyloxy group, a carbamoyl group which may be substituted, hydroxyl group, nitro group, cyano group, and an amino group which may be substituted,
characterized in that the process comprises the step of allowing a compound represented by the formula: N2CHCOR wherein R is the same as that defined above react with a compound represented by the formula: CH2xe2x95x90CXF wherein X is the same as that defined above in the presence of a catalyst comprising a metal atom selected from the group consisting of a transition metal of group 8, molybdenum, and copper, together with at least one chiral ligand selected from the group consisting of a carboxylic acid-type ligand, an amide-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, 1,3-diketone-type ligand, a Schiff base-type ligand, an oxazoline-type ligand, and a diamine-type ligand to preferentially produce a stereoisomer of the compound of the general formula (I) wherein the stereochemical configuration at the I-position is S-configuration.
According to preferred embodiments of the above invention, there are provided the aforementioned process which preferentially produces a stereoisomer of a compound of the general formula (I) wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom is in cis-configuration; the aforementioned process which preferentially produces a stereoisomer of the compound of the general formula (I) wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom is in trans-configuration; the aforementioned process wherein X is chlorine atom or bromine atom; the aforementioned process wherein R is a C1-10 alkyloxy group; the aforementioned process wherein R is a C1-6 alkyloxy group; and the aforementioned process wherein R is ethoxy group.
As preferred embodiments of the aforementioned invention, there are also provided the aforementioned process which is carried out in the presence of said catalyst containing at least one chiral ligand selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand; the aforementioned process which is carried out in the presence of a catalyst containing at least one chiral ligand selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand together with at least one ligand selected from the group consisting of a halogen-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, a 1,3-diketone-type ligand, a Schiff base-type ligand, and a carbon monoxide type ligand; the aforementioned process which is carried out in the presence of a catalyst containing at least one chiral ligand selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand together with at least one ligand selected from the group consisting of a halogen-type ligand, a phosphine-type ligand, and a carbon monoxide type ligand; and the aforementioned process which is carried out in the presence of said catalyst containing at least one chiral ligand selected from the group consisting of an oxazoline-type ligand and a diamine-type ligand.
As preferred embodiments of the aforementioned invention, there are further provided the aforementioned process which is carried out in the presence of the catalyst containing two or more identical chiral ligands selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand; the aforementioned process which is carried out in the presence of the catalyst containing the identical chiral ligands selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand; the aforementioned process which is carried out in the presence of the catalyst containing at least one carboxylic acid-type chiral ligand; the aforementioned process which is carried out in the presence of the catalyst containing two or more identical carboxylic acid-type chiral ligands; the aforementioned process which is carried out in the presence of the catalyst containing as ligands only identical carboxylic acid-type optically active ligands; the aforementioned process which is carried out in the presence of the catalyst containing at least one amide-type chiral ligand; the aforementioned process which is carried out in the presence of the catalyst containing two or more identical amide-type chiral ligands; the aforementioned process which is carried out in the presence of the catalyst containing as ligands only identical amide-type chiral ligands; the aforementioned process which is carried out in the presence of said catalyst containing cobalt, rhodium, iridium, ruthenium, palladium, molybdenum, copper, or iron as the metal atom; and the aforementioned process which is carried out in the presence of said catalyst containing rhodium as the metal atom. As preferred embodiments of the aforementioned invention, there are also provided the aforementioned process which is carried out in the presence of the catalyst containing at least one chiral ligand selected from the group consisting of an oxazoline-type ligand and a diamine-type ligand; the aforementioned process which is carried out in the presence of the catalyst containing copper as the metal atom; and the aforementioned process wherein a copper source is at least one substance selected from the group consisting of copper (I) trifluoromethanesulfonate [CuOSO2CF3] and copper (II) trifluoromethanesulfonate [Cu(OSO2CF3)2].
The first embodiment of the process of the present invention is characterized in that, where a compound of the general formula (II) represented by CH2xe2x95x90CXF and a compound of the general formula (III) represented by N2CHCOR are reacted to give a compound of the general formula (I), the process is carried out in the presence of the aforementioned specific catalyst to preferentially produce a stereoisomer of the compound of the general formula (I) wherein the stereochemical configuration at the 1-position is S-configuration (in the specification, among the carbon atoms constituting the cyclopropane ring, the carbon atom to which the substituent xe2x80x94COR binds is referred to as the carbon atom at the 1-position).
One embodiment of the present invention is characterized in that a stereoisomer of the compound of the general formula (I) is preferentially formed wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom are in cis-configuration (the term xe2x80x9ccis-configurationxe2x80x9d herein used means that the substituent represented by xe2x80x94COR and the fluorine atom on the cyclopropane ring are present on the same side of the plane provided by the cyclopropane ring). Another embodiment of the present invention is characterized in that a stereoisomer of the compound of the general formula (I) is preferentially formed wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom are in trans-configuration.
In each of the inventions mentioned above, the wording xe2x80x9ca stereoisomer is preferentially formedxe2x80x9d means that the produced amount of the desired stereoisomer as the target among the compounds of formula (I) exceeds those of the other stereoisomers. In the specification, this wording should be construed in its broadest meaning, which includes where the produced amount of the desired stereoisomer only slightly exceeds those of the other stereoisomers, and where only the desired stereoisomer is substantially produced, but excludes where the produced amount of the desired stereoisomer is completely the same as those of the other stereoisomer.
In the compounds represented by the general formula (I) and the general formula (II), X represents chlorine atom, bromine atom, or iodine atom. Among them, X may preferably be chlorine atom or bromine atom. As the compound of the above general formula (I), 2-chloro-2-fluorocyclopropanecarboxylic acid derivatives and 2-bromo-2-fluorocyclo-propanecarboxylic acid derivatives are preferred.
In the compounds of the general formula (I) and the general formula (III), R represents a C1-10 alkyloxy group (preferably a C1-6 alkyloxy group) which may have one or more halogen atoms or one or more C1-10 alkyloxy groups (preferably a C1-6 alkyloxy group);
an aralkyloxy group constituted by an aryl group which may be substituted and a C1-10 alkyloxy group (preferably a C1-6 alkyloxy group);
an aryloxy group having one or more aryl groups which may be substituted;
a C1-10 alkylthio group (preferably a C1-6 alkylthio group) which may have one or more halogen atoms;
an aralkylthio group constituted by an aryl group which may have a substituent(s) and a C1-10 alkylthio group (preferably a C1-6 alkylthio group);
amino group; or
a substituted amino group which has one or two substituents selected from the group consisting of a C1-10 alkyl group (preferably a C1-6 alkyl group), an aryl group which may be substituted, an aralkyl group constituted by an aryl group which may be substituted together with a C1-10 alkyl group (preferably a C1-6 alkyl group), and an acyl group.
In the above definition, substituents of the substituted aryl groups are selected from the group consisting of a halogen atom, a C1-10 alkyl group (preferably a C1-6 alkyl group), a C1-10 halogenoalkyl group (preferably a C1-6 halogenoalkyl group), a C1-10 alkyloxy group (preferably a C1-6 alkyloxy group), a carbamoyl group which may be substituted, hydroxyl group, nitro group, cyano group, and an amino group which may be substituted.
In the above definition of R, the alkyloxy group may be a straight chain-, a branched chain-, or a cyclic alkyl. As the C1-10 alkyloxy group, for example, methoxy group, ethoxy group, n-propoxy group, isopropoxy group, cyclopropoxy group, n-butoxy group, sec-butoxy group, tert-butoxy group, cyclobutoxy group, n-pentoxy group, n-hexoxy group, cyclohexyloxy group, levo-menthyloxy group or the like can be used. These C1-10 alkyloxy groups may be substituted with one or more halogen atoms (when the term xe2x80x9chalogen atomxe2x80x9d is herein referred to, the term is used so as to include any of fluorine atom, chlorine atom, bromine atom, and iodine atom unless specifically indicated), or with one or more C1-10 alkyloxy groups (for example, those exemplified above, preferably C1-6 alkyloxy groups). As the alkyloxy group represented by R, a straight chain- or branched chain-C1-6 alkyloxy group is preferred, and ethoxy group or methoxy group is particularly preferred.
The aralkyloxy group is constituted by an aryl group such as phenyl group and naphthyl group (which may be substituted) together with the C1-10 alkyloxy group mentioned above. Examples of the aralkyloxy group include, for example, benzyloxy group, diphenylmethyloxy group, and triphenylmethyloxy group. When the aralkyloxy group has two or more aryl groups, those aryl groups may be identical or different. The aryl group constituting the aryloxy group may be any one of aryl groups which may be substituted. For example, phenyl group or naphthyl group may suitably used. Examples of the aryloxy group include, for example, phenoxy group, 1-naphthoxy group, and 2-naphthoxy group.
The C1-10 alkylthio group and aralkylthio group correspond to the C1-10 alkyloxy group and aralkyloxy group explained above, respectively, in which the oxygen atom constituting the oxy group is replaced with a sulfur atom.
When R represents a substituted amino group, examples of a usable substituent on the amino group include a C1-10 alkyl group, an aryl group which may be substituted, an aralkyl group constituted by an aryl group which may be substituted together with a C1-10 alkyl group, and an acyl group. When two substituents bind to the amino group, they may be the same or different.
With regard to the substituents on the amino group mentioned above, the C1-10 alkyl group may be any one of straight chain-, branched chain-, or cyclic alkyl. For example, methyl group, ethyl group, n-propyl group, isopropyl group, cyclopropyl group, n-butyl group, sec-butyl group, tert-butyl group, cyclobutyl group, n-pentyl group, n-hexyl group, cyclohexyl group, or 1-menthyl group may be used. As the aryl group, phenyl group, naphthyl group, and the like can be used. The aralkyl group is constituted by an aryl group such as phenyl group or naphthyl group (which may be substituted) together with the aforementioned C1-10 alkyl group. For example, benzyl group, diphenylmethyl group, triphenylmethyl group can be used. As the acyl group, either of an aliphatic acyl group constituted by the aforementioned C1-10 alkyl group together with carbonyl group, or an aromatic acyl group constituted by an aryl group which may be substituted together with carbonyl group can be used. For example, acetyl group, benzoyl group and the like can be used.
With regard to the substituent explained above, a substituent selected from the group consisting of a halogen atom, the aforementioned C1-10 alkyl group, a C1-10 halogenoalkyl group being a C1-10 alkyl group substituted with one or more halogen atoms, the aforementioned C1-10 alkyloxy group, a carbamoyl group which may be substituted, hydroxyl group, nitro group, cyano group, and an amino group which may be substituted can be used as the substituent of the substituted aryl group. When the aryl group has two or more substituents, those substituents may be the same or different. When a substituted amino group and/or a substituted carbamoyl group is used as one or more substituents on the aryl group, the substituents on the amino group, those explained above as to the definition wherein R is a substituted amino group, may be used as substituents on the amino group and/or the carbamoyl group.
The process of the present invention is characterized in that the process utilizes a catalyst containing a metal atom selected from the group consisting of a transition metal of group 8, molybdenum, and copper, together with at least one chiral ligand selected from the group consisting of a carboxylic acid-type ligand, an amide-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, a 1,3-diketone-type ligand, a Schiff base-type ligand, an oxazoline-type ligand, and a diamine type ligand for the reaction of a compound of the formula (II) and a compound of the formula (III). As to the ligand of the catalyst, the ligand is specified in the specification based on the type of a functional group coordinating to the metal atom of the catalyst. For example, when carboxyl group in a ligand coordinates to a metal atom, the ligand is referred to as a carboxylic acid-type ligand. However, where a carboxylic acid ligand, for example, is referred to in the specification, one or more functional groups other than carboxyl group (e.g., one or more functional groups such as an alkyl group, an aryl group, an aralkyl group, and a heterocyclic group) may be present in the ligand. As to an amide-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, a 1,3-diketone-type ligand, a Schiff base-type ligand, an oxazoline-type ligand, and a diamine-type ligand, the wording should be interpreted similarly.
Among the catalysts comprising the aforementioned components, for example, the following catalysts are preferably used for the process of the present invention:
(a) the aforementioned catalyst which contains at least one chiral ligand which is selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand;
(b) the catalyst which contains at least one chiral ligand selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand, together with at least one ligand which is selected from the group consisting of a halogen-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, a 1,3-diketone-type ligand, a Schiff base-type ligand, and a carbon monoxide-type ligand;
(c) the catalyst which contains at least one chiral ligand which is selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand, together with at least one ligand selected from the group consisting of a halogen-type ligand, a phosphine-type ligand, and a carbon monoxide-type ligand;
(d) the catalyst which contains at least one chiral ligand which is selected from the group consisting of an oxazoline-type ligand and a diamine-type ligand; and the like.
Iron, nickel, rhodium, palladium, cobalt, iridium, ruthenium, and the like may preferably be used as the transition metal of group 8, and as a metal other than the transition metals of group 8, molybdenum or copper can be used. It is preferred that the valence of these metal atoms are divalent at forming the catalyst. Where a metal such as copper is used, the metal may be monovalent. Examples of preferred metal atoms include, for example, rhodium, palladium, cobalt, iridium, ruthenium, molybdenum, copper, and iron.
The catalyst used for the process of the present invention is characterized in that it contains at least one chiral ligand. The chiral ligand is selected from the group consisting of a carboxylic acid-type ligand, an amide-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, a 1,3-diketone-type ligand, a Schiff base-type ligand, an oxazoline-type ligand, and a diamine-type ligand, and preferably, the ligand is selected from the group consisting of a carboxylic acid-type ligand, an amide-type ligand, an oxazoline-type ligand, and a diamine-type ligand. When two or more chiral ligands coordinate to the aforementioned metal, it is preferable that each of the chiral ligands is structurally and optically identical. However, two or more different types of optically active ligands may coordinate to the metal.
For example, all of the ligands on the aforementioned metal may be chiral ligands selected from a carboxylic acid-type ligand and an amide-type ligand. Alternatively, for example, one or more chiral ligands among the ligands on the metal may be selected from the group consisting of a carboxylic acid-type ligand and an amide-type ligand, and the other one or more ligands may be selected from the group consisting of a halogen-type ligand, a phosphine-type ligand, an oxime-type ligand, a sulfonic acid-type ligand, a 1,3-diketone-type ligand, a Schiff base-type ligand, and a carbon monoxide-type ligand, preferably from the group consisting of a halogen-type ligand, a phosphine-type ligand, and a carbon monoxide-type ligand. In this case, the aforementioned ligands other than the carboxylic acid and the amide types may be chiral ligands.
As a compound for providing the chiral carboxylic acid-type ligand, for example, optically active amino acids or optically active carboxylic acids having one or more asymmetric carbons can be used. As the optically active amino acids, for example, D- or L-alanine, arginine, asparagine, aspartic acid, cysteine, cystine, histidine, hydroxylysine, hydroxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, thyroxine, tryptophane, tyrosine, valine, aminobutyric acid, citrulline, cystathionine, phenylglycine, methionine, norleucine, norvaline, glutamic acid, glutamine, penicillamine, pipecolic acid, 3,5-dibromotyrosine, 3,5-diiodotyrosine and other may be used.
As the optically active carboxylic acids, for example, 2-chloropropionic acid, 2-bromopropionic acid, 2-acetoxypropionic acid, 2,3-diaminopropionic acid, 2-phenylpropionic acid, 2-chloro-3-phenylpropionic acid, 2-hydroxy-3-phenylpropionic acid, 2-(6-methoxy-2-naphthyl)propionic acid, 3-acetylthio-2-methylpropionic acid, 2-amino-3-guanidinopropionic acid, 3-acetylthioisobutyric acid, 2-chlorobutyric acid, 2-chloro-3-methylbutyric acid, 3-hydroxybutyric acid, 2,4-diaminobutyric acid, 2-methylbutyric acid, 2-phenylbutyric acid, 3-phenylbutyric acid, 2-chloro-3-methylvaleric acid, 2-chloro-4-methylvaleric acid, menthoxyacetic acid, 2-methoxyphenylacetic acid, 2-methoxy-2-trifluoromethylphenylacetic acid, phenylsuccinic acid, shikimic acid, camphoric acid, mandelic acid, hexahydromandelic acid, monomenthyl phthalate, N-(xcex1-methylbenzyl)phthalic acid monoamide, 2-oxothiazolidine-4-carboxylic acid, 3-phenyllactic acid, lactic acid, 4-hydroxypyrroline, pyroglutamic acid, malic acid, 2-methylmalic acid, 2-benzamidecyclohexanecarboxylic acid, 3-methyladipic acid, tartaric acid and other may be used.
Among functional groups existing in the chiral amino acids or the chiral carboxylic acids mentioned above, functional groups other than the carboxyl group for coordinating to the metal atom (e.g., amino group) may be protected by means of a protective group available to those skilled in the art. As protective groups for amino group, for example, maleic anhydride, 2,3-dichloromaleic anhydride, phthalic anhydride, 3,6-dichlorophthalic anhydride, 4,5-dichlorophthalic anhydride, 3,6-difluorophthalic anhydride, 4,5-difluorophthalic anhydride, 3,4,5,6-tetrachlorophthalic anhydride, 3,4,5,6-tetrafluorophthalic anhydride, hexahydrophthalic anhydride, 1,2,3,6-tetrahydrophthalic anhydride, glutaric anhydride, 3-methylglutaric anhydride, itaconic anhydride, 1,8-naphthalic anhydride, succinic anhydride, tetrafluorosuccinic anhydride, 3,4,5,6-tetrahydrosuccinic anhydride, citraconic anhydride, 1-cyclopentene-1,2-dicarboxylic anhydride, cis-endo-5-norbornene-2,3-dicarboxylic anhydride, bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, formyl group, acetyl group, benzoyl group, trifluoroacetyl group, benzyloxycarbonyl group, methoxycarbonyl group, tert-butoxycarbonyl group, trifluoromethanesulfonyl group, p-toluenesulfonyl group and other may be used.
As a compound for providing the optically active amide-type ligand, examples include 3-acetamidopyrrolidine, 1-benzoyl-2-tert-butyl-3-methyl-4-imidazolidinone, 1-tert-butoxycarbonyl-2-tert-butyl-3-methyl-4-imidazolidinone, 4-amino-3-isoxazolidone, 1,5-dimethyl-4-phenyl-2-imidazolidinone, N-(3,5-dinitrobenzoyl)-1-phenylethylamine, 5-(hydroxymethyl)-2-pyrrolidinone, 4-isopropyl-2-oxazolizinone, 4-methyl-5-phenyl-2-oxazolizinone, 2-oxothiazolidine-4-carboxylic acid, 4-phenyloxazolidin-2-one, prolineamide, proline-2-naphthylamide, pyroglutamic acid ethyl ester, pyroglutamic acid 2-naphthylamide and other.
As a compound for providing the chiral oxazoline-type ligand, for example, an example includes the compounds set out below: 
wherein R1 represents a lower alkyl group having 1 to 5 carbon atoms or a phenyl group which may be substituted, and R2 represents hydrogen atom or methyl group.
As specific compounds for providing the chiral oxazoline-type ligand, examples include, compounds wherein the stereochemistry of each of the asymmetric carbon atoms bound by R1 is S-configuration, including 2,2xe2x80x2-methylenebis[(4S)-4-tert-butyl-2-oxazoline], 2,2xe2x80x2-isopropylidene-bis-[(4S)-4-tert-butyl-2-oxazoline], 2,2xe2x80x2-methylenebis[(4S)-4-isopropyl-2-oxazoline], 2,2xe2x80x2-isopropylidenebis[(4S)-4-isopropyl-2-oxazoline], 2,2xe2x80x2-isopropylidenebis[(4S)-4-benzyl-2-oxazoline] and other.
As a compound for providing the chiral diamine-type ligand, an example includes the compounds set out below: 
wherein R3 represents benzyl group, 2,4,6-trimethylphenylmethyl group, or diphenyl-methyl group.
As specific compounds for providing the chiral diamine-type ligand, examples include, compounds wherein the stereochemistry of each of the asymmetric carbon atoms bound by the phenyl group is R-configuration, including (1R,2R)-1,2-diphenyl-N,Nxe2x80x2-bis[2,4,6-trimethylphenylmethyl]-ethylenediamine, (1R,2R)-1,2-diphenyl-N,Nxe2x80x2-bisbenzylethylenediamine and other.
The halogen type-ligand, the phosphine-type ligand, the oxime-type ligand, the sulfonic acid-type ligand, the 1,3-diketone-type ligand, the Schiff basetype ligand, and the carbon monoxide-type ligand are well-known to those skilled in the art and can be appropriately chosen.
As examples of the catalyst preferably used for the process of the present invention, catalysts comprising divalent rhodium together with chiral carboxylic acid-type ligands are shown below. However, the catalysts used for the process of the present invention are not limited to those indicated below. 
As other examples of the catalyst preferably used for the process of the present invention, catalysts having chiral amide-type ligands are shown below. However, the catalysts used for the process of the present invention are not limited to those set out below. 
Those catalysts mentioned above can be prepared by, for example, a method comprising the steps of adding rhodium (II) acetate dimer and an excess amount of a carboxylic acid or an amide compound to chlorobenzene, and refluxing the mixture and then purifying the product (Callot, H. J. and Mets, F., Tetrahedron, 41, 4495, 1985). They can also be produced by refluxing a mixture of rhodium (II) chloride trihydrate, carboxylic acid compound, and sodium hydrogencarbonate in anhydrous ethanol under inert atmosphere, and then purifying the product (Demoncean, A., et al., Tetrahedron, 46, 3889, 1990). However, the catalysts used for the process of the present invention are not limited to those produced by the aforementioned preparing methods. It can be readily understood that the aforementioned catalysts can also be appropriately prepared by suitably altering or modifying the reaction conditions, reagents or other specified for the methods disclosed in the literatures.
Among the catalysts suitably used for the present invention, examples of catalysts containing one or more oxazoline-type ligands or diamine-type ligands together with copper include, for example, a catalyst obtainable from 2,2xe2x80x2-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline] and copper (I) trifluoromethane-sulfonate; a catalyst obtainable from 2,2xe2x80x2-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline] and copper (II) trifluoromethane-sulfonate; a catalyst obtainable from 2,2xe2x80x2-isopropylidenebis[(4S)-4-tert-butyl-2-oxazoline], copper (II) trifluoromethanesulfonate and phenylhydrazine; a catalyst obtainable from 2,2xe2x80x2-methylenebis[(4S)-4-tert-butyl-2-oxazoline] and copper (II) trifluoromethanesulfonate; a catalyst obtainable from (1R,2R)-1,2-diphenyl-N,Nxe2x80x2-bis[2,4,6-trimethylphenylmethyl]-ethylenediamine, copper (II) trifluoromethanesulfonate and phenylhydrazine and other. However, the catalysts used for the process of the present invention are not limited to those mentioned above.
For example, the process of the present invention can be carried out as explained below. The diazoacetic acid derivatives represented by the formula (III) can be prepared by a method well-known to those skilled in the art. For example, a diazoacetic acid ester and diazoacetic acid amide can be easily produced by subjecting respective corresponding compounds having an amino group to diazotization reaction. The 1-fluoro-1-haloethylenes represented by the formula (II) are generally of a lower boiling point, and they can be used after liquefaction at a low temperature or dissolution in an organic solvent. They can also be used under elevated pressure as required. For the reaction, examples of an applicable process include a process comprising the steps of adding a necessary amount of the aforementioned catalyst to an ethylene compound of the formula (II) or its solution, and then adding a compound of the formula (III) to the mixture; or a process comprising the steps of adding a compound of the formula (III) to an ethylene compound of the formula (II) or its solution, and then adding a necessary amount of the aforementioned catalyst to the mixture.
The above reaction can be carried out in the presence or absence of a solvent. When a solvent is used, types of the solvent are not limited so long as they, per se, are inert in the reaction. For example, aprotic solvents can be used, and preferably, aliphatic hydrocarbons, halogenated hydrocarbons, ethers and other can be used. More specifically, aliphatic hydrocarbons such as n-hexane, n-heptane, and cyclohexane; halogenated hydrocarbons such as dichloromethane and 1,2-dichloroethane; and ethers such as diethyl ether and tetrahydrofuran can be used. Among them, dichloromethane, n-heptane, or cyclohexane is most generally used.
Amount of the catalyst is not particularly limited. In general, the amount can be suitably chosen within a range of a so-called catalytic amount. For example, the aforementioned catalyst can be used in a molar amount of about 10% or less based on the molar amount of the compound of the general formula (III), preferably in a molar amount within a range of around 0.01-10%. The reaction may be carried out under cooling, at room temperature, or under warming. For example, the reaction may be carried out at a temperature in a range of from about xe2x88x92100xc2x0 C. to 100xc2x0 C., preferably from about xe2x88x9250xc2x0 C. to 50xc2x0 C. Reaction time may generally be in a range of from about 30 minutes to about 48 hours, usually in a range of from about 1 hour to 24 hours. The reaction may be carried out under elevated pressure by using a sealed vessel such as an autoclave.
According to the aforementioned process of the present invention, either a stereoisomer wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom are in cis-configuration, or a stereoisomer wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom are in trans-configuration can be preferentially prepared by suitably choosing the type of the catalyst used or other conditions. Those skilled in the art will readily understand that they can appropriately choose such catalyst by referring to the present specification.
A stereoisomer of a compound of the general formula (I) produced according to the aforementioned process of the present invention can be readily converted into a 2-fluorocyclopropanecarboxylic acid derivative by subjecting the stereoisomer to dehalogenation reaction (as to this reaction, fluorine atom is excluded from xe2x80x9chalogenxe2x80x9d) to replace the substituent X with hydrogen atom. Therefore, according to further embodiments of the present invention, there are provided a process for preparing (1S,2S)-2-fluorocyclopropanecarboxylic acid derivatives which comprises the steps of preparing a stereoisomer of the compound of the general formula (I) according to the aforementioned process; and then subjecting the resulting stereoisomer to dehalogenation to prepare a (1S,2S)-2-fluorocyclopropanecarboxylic acid derivative; and a process for preparing (1S,2S)-2-fluorocyclopropanecarboxylic acid derivatives which comprises the step of subjecting a stereoisomer of the compound of the general formula (I) prepared according to the aforementioned reaction to dehalogenation reaction without isolation or purification.
When the stereoisomer wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom is in cis-configuration is produced according to the process of the present invention, (1S,2S)-2-fluorocyclopropanecarboxylic acid can be prepared by carrying out a retention reaction as the dehalogenation reaction. On the other hand, when the stereoisomer wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom is in trans-configuration is produced according to the process of the present invention, (1S,2S)-2-fluorocyclopropanecarboxylic acid can be prepared by carrying out an inversion reaction as the dehalogenation reaction.
Methods for the dehalogenation are not particularly limited. For example, hydrogenolysis by using Raney nickel catalyst in the presence of hydrogen gas flow and a base is preferable (Japanese Patent Unexamined Publication (KOKAI) No. (Hei) 7-97353/1995). This dehalogenation proceeds as retention of configuration, and accordingly, it is preferred to employ this dehalogenation when the stereoisomer of the compound of the general formula (I) wherein the stereochemical configuration at the 1-position is S-configuration and the substituent represented by xe2x80x94COR and the fluorine atom is in cis-configuration is produced according to the process of the present invention.
Optical purity of the resulting 2-fluorocyclopropanecarboxylic acid derivative can be readily determined by means of, for example, a gas chromatographic analysis using an optically active capillary column after the 2-fluorocyclopropanecarboxylic acid derivative is converted into an ester compound. Alternatively, a liquid chromatographic analysis may also be applicable after the 2-fluorocyclopropanecarboxylic acid derivative is converted into an optically active amide compound such as a 1-phenylethylamide derivative.